Multi-Particle QM Homework: Equations & Attempt at Solution

  • Thread starter Thread starter binbagsss
  • Start date Start date
  • Tags Tags
    Qm
binbagsss
Messages
1,291
Reaction score
12

Homework Statement



Question attached:

multi-particle qm.png


Homework Equations



below

The Attempt at a Solution



I have completed this question and the needed commutator relation is that ##[a(x),a^+(x')]=\delta(x-x')##

However I have it all with the integral i.e.

##\int dx_1 dx_2 a^+(x_1)a^+(x_2) \Psi (x_1,x_2) | 0> ##

and

##\int dx_1 dx_2 a^+(x_1)a^+(x_2) \frac{-h^2}{2m}(\frac{\partial^2}{\partial x_1^2}+\frac{\partial^2}{\partial x_2^2} ) \Psi (x_1,x_2) |0> ## such terms etc

and am unsure of the final argument needed to explain why it holds without the integral.

Many thanks for your help.
 

Attachments

  • multi-particle qm.png
    multi-particle qm.png
    29 KB · Views: 1,016
Physics news on Phys.org
binbagsss said:

Homework Statement



Question attached:

View attachment 224316

Homework Equations



below

The Attempt at a Solution



I have completed this question and the needed commutator relation is that ##[a(x),a^+(x')]=\delta(x-x')##

However I have it all with the integral i.e.

##\int dx_1 dx_2 a^+(x_1)a^+(x_2) \Psi (x_1,x_2) | 0> ##

and

##\int dx_1 dx_2 a^+(x_1)a^+(x_2) \frac{-h^2}{2m}(\frac{\partial^2}{\partial x_1^2}+\frac{\partial^2}{\partial x_2^2} ) \Psi (x_1,x_2) |0> ## such terms etc

and am unsure of the final argument needed to explain why it holds without the integral.

Many thanks for your help.
It is hard to help without any details about your steps or the precise result of your final expression. I have the gut feeling that you applied H to Psi but that maybe you used the same coordinates in both H and Psi, which can lead to a problem. But again, more details would be helpful.
 
Thread 'Need help understanding this figure on energy levels'
This figure is from "Introduction to Quantum Mechanics" by Griffiths (3rd edition). It is available to download. It is from page 142. I am hoping the usual people on this site will give me a hand understanding what is going on in the figure. After the equation (4.50) it says "It is customary to introduce the principal quantum number, ##n##, which simply orders the allowed energies, starting with 1 for the ground state. (see the figure)" I still don't understand the figure :( Here is...
Thread 'Understanding how to "tack on" the time wiggle factor'
The last problem I posted on QM made it into advanced homework help, that is why I am putting it here. I am sorry for any hassle imposed on the moderators by myself. Part (a) is quite easy. We get $$\sigma_1 = 2\lambda, \mathbf{v}_1 = \begin{pmatrix} 0 \\ 0 \\ 1 \end{pmatrix} \sigma_2 = \lambda, \mathbf{v}_2 = \begin{pmatrix} 1/\sqrt{2} \\ 1/\sqrt{2} \\ 0 \end{pmatrix} \sigma_3 = -\lambda, \mathbf{v}_3 = \begin{pmatrix} 1/\sqrt{2} \\ -1/\sqrt{2} \\ 0 \end{pmatrix} $$ There are two ways...
Back
Top